cxgb4: fix possible deadlock

t4_wr_mbox_meat_timeout() can be called from both softirq
context and process context, hence protect the mbox with
spin_lock_bh() instead of simple spin_lock()
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/t4_hw.c

@@ -317,9 +317,9 @@ int t4_wr_mbox_meat_timeout(struct adapter *adap, int mbox, const void *cmd,
 	 * wait [for a while] till we're at the front [or bail out with an
 	 * EBUSY] ...
 	 */
-	spin_lock(&adap->mbox_lock);
+	spin_lock_bh(&adap->mbox_lock);
 	list_add_tail(&entry.list, &adap->mlist.list);
-	spin_unlock(&adap->mbox_lock);
+	spin_unlock_bh(&adap->mbox_lock);
 
 	delay_idx = 0;
 	ms = delay[0];
@@ -332,9 +332,9 @@ int t4_wr_mbox_meat_timeout(struct adapter *adap, int mbox, const void *cmd,
 		 */
 		pcie_fw = t4_read_reg(adap, PCIE_FW_A);
 		if (i > FW_CMD_MAX_TIMEOUT || (pcie_fw & PCIE_FW_ERR_F)) {
-			spin_lock(&adap->mbox_lock);
+			spin_lock_bh(&adap->mbox_lock);
 			list_del(&entry.list);
-			spin_unlock(&adap->mbox_lock);
+			spin_unlock_bh(&adap->mbox_lock);
 			ret = (pcie_fw & PCIE_FW_ERR_F) ? -ENXIO : -EBUSY;
 			t4_record_mbox(adap, cmd, size, access, ret);
 			return ret;
@@ -365,9 +365,9 @@ int t4_wr_mbox_meat_timeout(struct adapter *adap, int mbox, const void *cmd,
 	for (i = 0; v == MBOX_OWNER_NONE && i < 3; i++)
 		v = MBOWNER_G(t4_read_reg(adap, ctl_reg));
 	if (v != MBOX_OWNER_DRV) {
-		spin_lock(&adap->mbox_lock);
+		spin_lock_bh(&adap->mbox_lock);
 		list_del(&entry.list);
-		spin_unlock(&adap->mbox_lock);
+		spin_unlock_bh(&adap->mbox_lock);
 		ret = (v == MBOX_OWNER_FW) ? -EBUSY : -ETIMEDOUT;
 		t4_record_mbox(adap, cmd, size, access, ret);
 		return ret;
@@ -418,9 +418,9 @@ int t4_wr_mbox_meat_timeout(struct adapter *adap, int mbox, const void *cmd,
 			execute = i + ms;
 			t4_record_mbox(adap, cmd_rpl,
 				       MBOX_LEN, access, execute);
-			spin_lock(&adap->mbox_lock);
+			spin_lock_bh(&adap->mbox_lock);
 			list_del(&entry.list);
-			spin_unlock(&adap->mbox_lock);
+			spin_unlock_bh(&adap->mbox_lock);
 			return -FW_CMD_RETVAL_G((int)res);
 		}
 	}
@@ -430,9 +430,9 @@ int t4_wr_mbox_meat_timeout(struct adapter *adap, int mbox, const void *cmd,
 	dev_err(adap->pdev_dev, "command %#x in mailbox %d timed out\n",
 		*(const u8 *)cmd, mbox);
 	t4_report_fw_error(adap);
-	spin_lock(&adap->mbox_lock);
+	spin_lock_bh(&adap->mbox_lock);
 	list_del(&entry.list);
-	spin_unlock(&adap->mbox_lock);
+	spin_unlock_bh(&adap->mbox_lock);
 	t4_fatal_err(adap);
 	return ret;
 }